Humidifier and hollow yarn body to be used therefor

ABSTRACT

A humidifier ( 5 ) includes upper and lower water tanks ( 7 ) and ( 8 ) supported by a support frame ( 6 ). In a space between the upper and lower water tank, a plurality of hollow yarn bodies ( 1 ) are arranged in communication with upper and lower water tanks. The hollow yarn body is constructed of a parens yarn ( 2 ) of the hollow and a thin metal wire ( 3 ) connected to the power source thereof and wound around the hollow yarn body.

TECHNICAL FIELD

The present invention relates to a humidifier which forms a part of anair and humidity control system of an air conditioning system of thetype suitable for semiconductor fabrication plants and clean rooms, andwhich can control humidification with super high precision. Theinvention also relates to a hollow yarn as a humidifying material to beemployed in the humidifier.

BACKGROUND ART

A conventional type of humidifier is disclosed in Japanese ExaminedUtility Model Publication (Kokoku) No. Heisei 4-31476. The humidifiershown in FIG. 7, is such that water is supplied from an illustratedwater supply pipe to a water supply pan a. This water is absorbed by afilter material b of a humidifying element c and penetrates downwardlythrough the humidifying element c. The humidifying element c is arrangedso that the filter materials b have a plate-shaped configuration, areadhered on both side surfaces of a metal case e which has an internalhollow space d. Within the internal hollow space d of the case e of thehumidifying element c, is a heater f. By energizing of this heater f,the temperature within the hollow space of the humidifying element c israised. Accordingly, the filter materials b fixed on the humidifyingelement c are heated. This evaporates the water which has penetratedinto the filter material b and humidifies the air.

FIG. 8 shows another type of conventional humidifier. In thisarrangement, a water reservoir h is connected to a water supply pipe g,is placed within a warmer box j. A “throw-in” type metal heater i isdisposed in the water reservoir h. The water in the water reservoir h isheated by the metal heater i to the level whereat it evaporates and isdischarged through an evaporation opening k provided at the upperportion of the water reservoir h to humidify the external air. When thewater amount in the water reservoir h is reduced by evaporation, a waterlevel monitoring sensor m actuates an electromagnetic valve n to returnthe water to its original level.

The first of the above-mentioned prior art arrangements encounters thefollowing drawbacks.

(1) With this humidifying technique, the water is evaporated from thesurface of the humidifying element c by transmitting heating energy ofthe-heater f through heat transmission in order of “heaterf→environmental air→case e→filter material b→water”. Namely, this methodindirectly heats the water.

In addition to overheating and assuring a certain extent of water vaporamount, a given amount of water has to be stored in the filter materialb. Therefore, the filter material b has to be relatively large. Thisinhibits down-sizing and inherently produces large thermal inertia.

Accordingly, a long period is required from the initiation of heating bythe heater to the actual evaporation of the water. Also, when theevaporation amount is desired to be varied, a long lag time occursbetween the change in heating and the variation of the evaporation.Therefore, humidification control within a short period is difficult.

Furthermore, because of the indirect heating, precise water evaporationvolume cannot be achieved.

(2) Since water supply for the filter material b is achieved by thepenetration of water into the filter material b from the water supplypan a, the water propagates from the upper portion where the watersupply pan a is located, down to the lower portions.

Accordingly, there is a tendency that there is an insufficient supply ofwater at the lower portions of the filter b. Therefore, once evaporationof the water is initiated by heating with the heater i, the amount ofwater in the filter material b can become locally deficient and cancause abnormally high temperature regions. Under such conditions, thefilter material b may be thermally damaged and, in turn, heat the airpassing through the humidifying apparatus.

Additionally, since the water supply is achieved by penetration of waterthrough the filter material b, it is difficult to accurately control theamount of water supplied into the air. It is also possible that theheating energy by the heater exceeds the amount of water which canactually undergo evaporation. Accordingly, the excessive heating mayheat the environmental air of the humidifying element c or damage thefilter material b.

Due to the possibility of causing heating of the air passing through thehumidifier, it is difficult to realize ideal constant temperaturehumidification for humidifying without heating the environmental air.Accordingly, it is difficult to control the temperature and humidify ofthe air with high precision.

The second of the above-discussed prior art arrangements suffers fromthe following problems.

(1) Since all of the water in the water reservoir h has to be heated,thermal inertia is significantly large. Accordingly, start-upcharacteristics from initiation of heating to actual evaporation ispoor. Furthermore, when variation of the evaporation amount is desired,there is inherent long time lag from variation-of the heating amount ofthe heater i to the variation in the evaporation amount. Accordingly,with this arrangement, precise evaporation amount control is notpossible.

(2) Since a relatively large amount of water has to be retained in thewater reservoir, a large volume water reservoir h is necessary.Accordingly, the humidified device cannot be rendered compact.

(3) When the water in the water reservoir h is reduced to apredetermined extent by evaporation of the water, the water levelmonitoring sensor detects this and opens the electromagnetic valve n tosupply more water. Therefore, due to the supply of cold water, thetemperature of the water reservoir h is lowered and causes a fluctuationin the evaporation amount. Accordingly, precise evaporation amountcontrol is difficult.

Therefore, it is an object of the present invention to provide ahumidifier which can quickly perform large scale humidification, can becontrolled with high precision, and can be compactly constructed. It isa further object of the invention to provide a humidifier which featuresa hollow yarn body which is extremely durable, which permitssignificantly increased water evaporation from the surface, and whichfacilitates control of the evaporation amount. Also, Japanese UnexaminedUtility Model Publication No. 62-117437 discloses a humidifying methodemploying a heater wire. In the disclosed construction, the heater wireis wound around or inserted into a hollow tube formed of a “GOATEX”brand blended product of nylon and polyurethane which is known for itshigh water repellent property with water vapor permeability. The“GOATEX” brand product utilizes a hydrophobic property of the blendedyarn for achieving the water repellent property of the cloth. Therefore,in the shown construction, the heater wire heats all of the water withinthe hydrophobic and vapor permeable hollow tube. When the heater wire iswound on the outer periphery of the hollow tube, the heater wire mustheat the water within the hollow tube via the peripheral wall which isheat non-conductive. Therefore, it takes a long period of time forheating and, thus, a response from initiation of a power supply for themetal wire to beginning the evaporation of the water is quite low.Furthermore, the amount of the water to be heated by the metal wire asthe heater wire is much greater than that in the case of a thin waterfilm, so that thermal inertia is substantially large requiring a longperiod of time for varying the water evaporation amount from a variationof the heating amount. In addition, the water vapor generated by heatingthe water within the hollow yarn passes the wall portion of the hollowtube. For a large resistance of the wall portion of the hollow yarn tothe water vapor, it is not possible to supply the water vaporcorresponding to the discharge amount of the water. Therefore, the vaporamount to be discharged to the atmosphere for conditioning theenvironmental air cannot be accurately controlled.

SUMMARY OF THE INVENTION

In order to accomplish the above-mentioned and other objects, accordingto one aspect of the invention, there is provided a humidifiercharacterized by:

upper and lower water tanks supported by a support frame, a plurality ofhollow yarn bodies which are arranged in communication with the upperand lower water tanks, and which each have a thin metal wire that isconnected to a power source, wound on the external surfaces thereof.

With the construction set forth above, by passing the water through thehollow yarn body and supplying electric power to the metal wire, thewater effusing to the external peripheral wall surface of the hollowyarn bodies is heated and evaporated. In this case, the water can bedirectly and uniformly distributed through the yarn of each hollow yarnbody and directly heated by the heater. Accordingly, supply of the watercan be achieved quickly and in large amounts. Also, the water supplyamount can be precisely controlled. In addition, a humidifier having acapacity to supply a large amount of water, can be rendered compactthrough the use of the hollow yarn bodies. Therefore, the humidifieremploying such hollow yarn bodies can perform humidification quickly andin large amounts, and the humidification control can be achieved withhigh precision.

According to a second aspect of the invention, there is provided ahollow yarn body formed by winding a thin metal wire which acts as aheating element on the outer periphery of a hollow yarn body formed ofwoven of fiber.

Preferably, the material of the fiber forming said hollow yarn may be amaterial having both heat resistance and hydrophilic properties. Thematerial can be selected among polyester, polyamide, aromatic polyamide,polyimide, glass, quartz glass, alumina, silica alumina, acryl,polypropylene, aromatic polyester, cellulose and so forth.

Also, on the external peripheral surface of the hollow yarn, one or moremetal wires which serve as heating elements may be wound in spiral orhelical fashion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of thepreferred embodiment of the invention, which, however, should not betaken to be limitative to the present invention, but for explanativepurposes.

In the drawings:

FIG. 1 is a section showing a humidifier according to the presentinvention;

FIG. 2 is a perspective view showing a hollow yarn body according to thepresent invention;

FIG. 3 is an explanatory illustration showing the humidifying functionof a hollow yarn body;

FIG. 4 is an enlarged section showing the condition where a water filmis formed on the external wall surface of the hollow yarn body;

FIG. 5 is a chart showing the humidity versus power supply amountachieved with the humidifier according to the present invention;

FIG. 6 is a chart showing the performance of the humidifier in terms ofthe humidity of the humidified air versus time.

FIG. 7 is a section showing a part of the first prior art discussed inthe opening paragraph s of the disclosure; and

FIG. 8 is a fragmentary section showing the second prior art discussedin the opening paragraphs of the disclosure.

BEST MODE FOR IMPLEMENTING THE INVENTION

The preferred embodiment of a humidifier and a hollow yarn bodyaccording to the present invention will be discussed with reference toFIGS. 1 to 5.

(1) Description of Humidifier Employing Hollow Yarn Body

FIG. 1 shows a humidifier 5 constructed with a large number of hollowyarn bodies 1.

Between opposing wall portions 7 a and 8 a of upper and lower watertanks 7 and 8 which are supported on a support frame 6, are a largenumber of hollow yarn bodies 1. The upper and lower ends of each hollowyarn body 1 are respectively communicated with the water tanks 7 and 8.Both wall portions 7 a and 8 a are formed of an electrically conductivematerial. A power source 9 is connected across the wall portions 7 a and8 a so that electric power is supplied to a metal wire 3 serving as aheater for each individual hollow yarn body 1. Between the wall portions7 a and 8 a, an air flow passage 10 is defined. Each of the hollow yarnbodies 1 is exposed to the air flowing through the air flow passage 10.

(2) Description of a Hollow Yarn Body

As shown in FIG. 2, each of the hollow yarn bodies 1 is constituted by ahollow yarn weave or substrate 2 and the thin metal wire 3 which iswound around the external peripheral wall surface of the hollow yarn 2and which serves as a heater. The hollow yarn substrate 2 has a porousyarn wall formed by weaving long fiber filaments together. For thepurposes of description, the inner side of the hollow portion of thehollow yarn wall will be referred to as internal peripheral wall surface2 a and the outer side will be referred to as external peripheral wallsurface 2 b.

The long fiber filament forming the hollow yarn 2. is

(1) required to have high hydrophilic property for permittingpenetration of a large amount of water; (2) required to have a heatresistance since the metal wire 3 is wound directly on the externalperiphery; and is (3) required to exhibit a flexibility which allowsstranding and weaving of the hollow yarn 2.

As shown in FIGS. 3 and 4. when the water passes through the hollowspace of the hollow yarn body 1 due to the high hydrophilic property ofthe long fiber filament forming the hollow yarn 2. the water, under theinfluence of its own surface tension, penetrates into the hollow yarnwall from the internal peripheral wall surface 2 a toward the externalperipheral wall surface 2 b along the surface of the filaments. Then,due to the surface tension of the water, a thin water film 4 is formedon the external peripheral wall surface 2 b of the hollow yarn 2 andover the surface of the metal wire 3 wound around the externalperipheral wall surface 2 b. Thus, when the metal wire 3 is heated bypower supply, the water forming the water film 4 is quickly heated andevaporated. At this time, by blowing dry air over the hollow yarn body1. the dry air becomes humidified through the inclusion of the watervapor.

The amount of water evaporation can be controlled by regulating thepower supply (heating amount) to the metal wire 3. The power supply canbe regulated based on the amount and a temperature of air to be blownover each hollow yarn body 1. the initial humidity of the air, etc.

An absolute water evaporation amount by the hollow yarn body 1 can beadjusted by varying the structure of the hollow yarn 2 (internaldiameter, external diameter, hollow yarn wall thickness, weaving densityand so forth), and hydrophilic property of the long fiber filament,manner of winding of the metal wire and so forth.

It should be appreciated that since the hollow yarn 2 is prepared byweaving long, thin fiber filaments, it is possible that even a smallamount of impurity can cause blockage. Therefore, it is preferred thatthe water which is supplied into the hollow space of the hollow yarn 2is pure or distilled water.

As shown in FIG. 4, the hollow yarn 2 is fabricated from a plurality ofheat resistive, hydrophilic and flexible long fiber filaments which arewoven into string form and by weaving a plurality of stranded strings intwill weave, plain weave or other weaving pattern, into hollowconfiguration. The hollow yarn 2 has an external diameter in a range of0.5 to 5.0 mm and an internal diameter in a range of 0.4 to 4.5 mm.

The long fiber filament is required to have a flexibility sufficient forstranding and weaving during the fabrication process.

As the material which have hydrophilic property, heat resistance andflexibility, acryl, polyester, polypropylene, polyamide, aromaticpolyamide, polymide, aromatic polyester, cellulose, glass fiber, ceramicfiber made of alumina and so forth are suitable.

The metal wire 3 to be wound around the hollow yarn 2 has a diameter ina range of 0.008 to 0.1 mm and as the material thereof, metals forheater, such as copper, stainless, tantalum, nichrome, titanium, nickel,platinum, gold and so forth are suitable.

The metal wire 3 is wound around the hollow yarn 2 in spiral fashion inthe case of single wire, and in alternately intersecting fashion in thecase of two or more wires (e.g., eight wires).

In connection with the winding of the metal wire 3. if a gap occursbetween the external peripheral surface of the hollow yarn 2 and themetal wire 3. the heat energy produced by power supply cannot acteffectively and can be a cause of local heating which inhibits precisehumidity control. Accordingly, it is preferred to minimize any gapswhich may form.

Furthermore, when the hollow yarn 2 is fabricated by a weaving patternsuch as twill weaving, the hollow yarn 2 may be expanded when a vertical(longitudinal) force is applied. Such hollow yarn 2 can therefore beinstalled in the humidifier 5 with stretching in the longitudinaldirection. In this case however, if the hollow yarn 2 is expanded,blocking of the pore of the hollow yarn 2 or reducing of the hollow yarnwall thickness or variation of the internal and external diameter of thehollow yarn 2 may be caused. Also, if the external diameter is reduced,a gap may be defined between the external wall of the hollow yarn andthe metal wire 3 wound around the external wall of the hollow yarn maybe formed to degrade tightness of fitting of the metal wire against thehollow yarn body. When such a situation occurs, humidificationperformance of the hollow yarn 1 is lowered and high precisionhumidification control becomes impossible.

However, the expansion in the longitudinal direction can be reduced byincreasing number of metal wires 3 wound in alternately intersectingmanner on the hollow yarn 2. Accordingly, it is advisable to use atleast a minimum number of wires 3 which can suppress expansion of thehollow yarn 2 in the longitudinal direction.

It should be appreciated that when the metal wires 3 are wound inalternately intersecting manner, the intersecting metal wires 3 mutuallydepress the other onto the external peripheral surface of the hollowyarn 2, and it is unnecessary to use a bond for preventing the formationof gaps between the external peripheral surface of the hollow yarn 2 andthe metal wires 3. In such instances, the heat of the metal wires can betransmitted to the water without being blocked by the bond. Also, sincesuch a bond should not be permitted to enter into the hollow yarn in amanner which invites blocking of the woven body, winding of the metalwire in an alternately intersecting manner is advantageous.

By employing the hollow yarn body 1 as set forth above, the followingfeatures may be attained.

(1) despite a compact size, evaporation (humidification) of largeamounts of water can be performed;

(2) the change in water evaporation in response to power supplyvariation becomes very high;

(3) water evaporation control through power supply control isfacilitated (proportional controlcan be performed) and humidificationcontrol can be performed with high precision and high stability;

(4) the range of water evaporation (humidification) control is widened;

(5) high security is provided ; and

(6) constant temperature humidification becomes possible.

As set forth above, in order to perform humidification, the water ispast through the hollow portion of the hollow yarn 2 and power isbrought into contact with the metal wire 3 to cause evaporation of thewater. By introducing the generated water vapor into the dry air, thedry air can be humidified.

Here, the principle of penetration of the water within the hollow yarn 2and the principle of evaporation of the penetrated water will bediscussed.

By making the long fiber filament forming the hollow yarn 2 from amaterial having a high hydrophilic property, wetting ability of thehollow yarn 2 to be water can be maintained at a high level. Namely,when the water is past through the hollow spaces in the hollow yarn 2.the water penetrates from the internal peripheral wall surface 2 a tothe external peripheral wall surface 2 b through the hollow yarn wall.This is caused by transmission of water along the surface of thefilament under capillarity action. Then, the water which reaches theexternal peripheral wall surface 2 b forms a thin water film 4 on theexternal peripheral wall surface 2 b of the hollow yarn 2 and on themetal wires 3 wound on the external peripheral wall surface due to itsown surface tension.

At this time, by heating the metal wires 3 by supplying power thereto,the water film 4 is converted into water vapor. Thus, the water formingthe film 4 is directly heated on the surface of the metal wires 3 andinstantly evaporated.

Even when the water is evaporated on the external peripheral wallsurface 2 b and the metal wire 3. since the long fiber filament has ahigh hydrophilic property, water is supplied from the internalperipheral wall surface 2 a to the external peripheral wall surface 2 bin continuous manner. Thus, as the water evaporates from the surface ofthe metal wire 3. it is continuously replenished.

In addition, the uniform supply of the water to the external peripheralwall surface 2 b can be achieved. As the water supply is achieved bycapillary action, no localized lack or excess of water will occur.Accordingly, the water can be stably and uniformly supplied to thesurface of the external peripheral wall surface 2 b and the surface ofthe metal wire 3.

The hollow yarn body 1 according to the present invention is formed bywinding thin metal wire 3 on thin hollow yarn 2. Therefore, the surfacearea of the metal wire 3 for causing evaporation of the water isrelatively large. Also, the hollow yarn 2 serving to supply the water iswoven from a large number of very thin long fiber filaments.Accordingly, the surface area of the long fiber filaments for conveyingthe water by capillary action is sufficient to ensure the supply ofwater.

For the two reasons set forth above, while the hollow yarn body 2 can befabricated into compact size, large amount of water supply and largeamount of evaporation of water can be certainly achieved.

Furthermore, since the evaporation of the water is performed on thesurface of the metal it can be performed by “direct heating”. Also, itis sufficient to supply the water from the inside of the hollow yarn 2in the amount necessary for evaporation. Therefore, it becomesunnecessary to store a large amount of water in the humidifying elementc as in the previously discussed prior art. Also, the water reservoir has required in the latter prior art becomes unnecessary. Furthermore,since the long fiber filament has a high hydrophilic property, thepenetration of the water from the internal peripheral wall surface 2 ato the external peripheral wall surface 2 b of the hollow yarn 2 is veryrapid. Accordingly, a vessel to store the water. is substantiallyunnecessary. Therefore, the wall of the hollow yarn can be thin. Thus,the hollow yarn 2 can be made compact.

With the three reasons set forth above, the hollow yarn body 1constituted of the hollow yarn 2 and the metal wire 3 c can providelarge evaporation amount while the overall humidifier can be madecompact.

Further, as set forth above, evaporation of water is caused by directheating of the water at the surface of the metal wire 3. Therefore, heatis not transmitted through a plurality of stages, such as “heaterf→environmental air→case e→filter material b→water” as in the previouslydiscussed prior art. Heating of a large amount of water by an immersedheater, as in the second of the above-discussed prior art arrangement,is not necessary.

In the hollow yarn body 1 according to the present invention, the metalwire 3 only heats the water forming the thin film 4 on the surface ofthe metal wire to instantly cause evaporation of the water. Namely, theenergy of the metal wire 3 is directly transmitted to the water.Accordingly, the humidifier employing the hollow yarn body 1 accordingto the present invention exhibits a high response speed and quicklystarts evaporating water following the supply of electrical power.

Furthermore, since the film of water present on the surface of the metalwire 3 is quite thin and is formed by the effect of surface tension,the-thermal inertia caused by the metal wire 3 and the water forming thethin film 4 on the surface of metal wire, is quite small.

Therefore, by varying the amount of heating, the evaporation amount canbe varied instantly. Accordingly, when the evaporation amount of thewater is desired to be varied, it can be achieved by varying powersupply for the metal wire 3. The response of variation of theevaporation amount of the water relative to variation of the heatingamount is quite high.

As mentioned above, what is associated with evaporation of the water isthe temperature of the metal wire 3 and the quite small amount of wateron the surface of the metal wire 3. Accordingly, water evaporationamount control by power supply can be performed easily (can be performedproportional control) with high precision.

Also, supply of the water to the external peripheral surface 2 b of thehollow yarn is performed from the overall internal peripheral wallsurface 2 a to the overall external peripheral wall surface 2 b and bythe capillary effect. Therefore, localized shortages of water areprevented as compared with the former prior art. Accordingly, the watercan be constantly, stably and uniformly supplied to the externalperipheral wall surface. Also, the metal wire 3 can be uniformly heated.

Accordingly, when the water amount and the heating are uniform,proportional control with these parameters can be performed and thuspermits high precision and stable control.

As set forth above, the humidifier 5 employing the hollow yarn body 1according to the present invention, can evaporate large amounts ofwater. Furthermore, it is possible to induce only a small amountevaporation by controlling the power supply amount. Accordingly, thewater evaporation amount (humidifying amount) can be arbitrary setanywhere between a large amount and a small amount. Namely, a humiditycontrol range can be quite wide.

As set forth above, the water can be constantly and uniformly suppliedto the external peripheral wall surface 2 b with stability, localshortages of water will never be avoided. Accordingly, abnormal localheating as in the former prior art will be avoided to assure safeoperation.

It is possible to perform control so that all of the heat energygenerated by power supply to the metal wire 3 forms water vapor.Accordingly, no extraneous heat energy will be imparted to the airpassing through the humidifier by the metal wire 3. Namely, constanttemperature humidification which results only in humidification can beperformed.

Next, discussion will be given for an example of implementation of thehumidifier 5 with the construction shown in the following table I.

TABLE I Embodi- Embodi- Embodi- CONSTRUCTION ITEM ment 1 ment 2 ment 3Hollow Hollow Long Fiber Polyester Heat Silica Yarn Yarn FilamentResistive Almina Body Material Glass Fiber Long Fiber 250 denyl ← 10μFilament Thickness Number of 48 ← 1000 Filament filaments filamentsForming String Number of 48 ← 24 String strings strings Forming HollowYarn Weaving Twill ← ← Pattern Hollow Yarn 1.6 mm ← 2.0 mm ExternalDiameter Hollow yarn 1.0 mm ← 1.2 mm Internal Diameter Metal MaterialStainless ← Nichrome Wire Thickness 0.03 mm ← 0.05 mm Number 8 ← 4Winding Alternately ← ← Pattern Inter- secting Electrical 3.5 Ω/cm 6.5Ω/cm 4.7 Ω/cm Resistance Humidi- Con- Hollow Yarn 307 cm² ← ← fierstruc- Body External tion Surface Area Hollow Yarn 612 cm ← ← BodyOverall Length Hollow Yarn 36 ← ← Body Number Humidifying FIGS. 5, 6 ←Performance

(Embodiment 1)

With the construction shown in the table I, the hollow yarn body 1 andthe humidifier 5 were prepared. The humidifying performance of thehumidifier thus constructed is shown in FIGS. 5 and 6.

In FIG. 5, there is shown a relationship of the achieved humidifyobtained by varying the power supply amount when initial humidity is19%, and air of 20° C. and 30° C. is past through the humidifier 5. Thevalue in the parenthesis represents water evaporation amount from thehumidifier at that time.

As can be clear from FIG. 5, by proportional control of the power supplyto the metal wire 3. the water evaporation amount can be accuratelycontrolled. At this time, for all temperatures of the air passingthrough the humidifying device, proportional control of the power supplyamount is possible. Also, the water evaporation amount is varieddepending upon respective set values. observing the water evaporationamount, at 30° C. and 60%, for example, 2,500 gr/Hr was achieved. This,it can be appreciated that the present invention permits largeevaporation amount with a compact device.

When 3000 durability test was performed, no variation of thecharacteristics occurred.

FIG. 6 shows the elapsed time when air having initial humidify of 19%and initial temperature of 30° C. is passed through the humidifier underthe conditions wherein the achieved humidity is controlled at 30% and60%.

As can be seen from FIG. 6, the desired humidity was achieved afterapproximately 2 seconds from setting of the power supply amount toachieve a humidity 30%. Also, as shown, it takes approximately 2 secondsto vary the humidity from 30% to 60%.

As set forth above, it should be appreciated that response speed fromsetting of the humidity to achievement of the set humidity is quitehigh.

Furthermore, in observation of the achievement condition, it fallswithin a range of ±0.1%. This, high precision humidity control can beachieved.

(Embodiment 2)

With the construction shown in the embodiment 2 in the foregoing tableI, the hollow yarn body 1 and the humidifier 5 were prepared. Thehumidifying performance of thus prepared humidifier 5 was substantiallythe same as the embodiment 1. Here, the heat resistant glass having MgO,Al₂O₃, SiO₂ as primary component was used.

In this embodiment, in order to check the safety of the invention upon atemporary failure of the water supply or loss of air flow, supply waterto the humidifier 5 was cut off and power at 7OW (252OW for overallhumidifier) per each hollow yarn body 1 was supplied for 100 hours. As aresult, while the hollow yarn 1 became heated to approximately 400° C.to 600 ° C. no melting or deformation of the hollow yarn was notobserved. Accordingly, it should be appreciated that the hollow yarnbody 1 is superior in viewpoint of heat resistance and safety.Thereafter, characteristics of the power supply amount and thehumidifying control were checked with the water supply re-established.The performance of the device was satisfactory.

(Embodiment 3)

Also, with the construction shown in the embodiment 3 of the foregoingtable I, the hollow yarn body 1 and the humidifier 5 were prepared.Here, as silica almina, one containing Al₂O₃ and SiO₂ as primarycomponent was used.

In this embodiment, in order to check durability, with supply water tothe humidifier 5. power was supplied at 3000W for 3000 hours. At thistime, the humidification amount of 3800 gr/Hr remained constant for 3000hours and no variation of the characteristics was observed. Accordingly,it has confirmed that the shown embodiment of the humidifier 5 has highdurability.

On the other hand, in order to check security upon temporary failure ofthe water way, with no supply water to the humidifier 5. power at 7OW(252OW for overall humidifier) per each hollow yarn body 1 was suppliedfor 150 hours. As a result, while the hollow yarn 1 achieved hightemperature of approximately 400° C. to 600° C. no melting ordeformation of the hollow yarn was caused. Accordingly, it should beappreciated that the hollow yarn body 1 is superior in viewpoint of heatresistance and security. Thereafter, characteristics of the power supplyamount and the humidifying control were checked by re-establishing thewater supply. The performance did not differ from that at initial state.

As will be clear from the results of the embodiments 1, 2 and 3. thehumidifier 5 according to the present invention can quickly generatelarge amount of water vapor to permit quick and high precisionhumidification.

It should be noted that as demonstrated by embodiments 2 and 3. hollowyarn can withstand heat for a long period even in the state where nowater is supplied. It is also possible to employ the device as a heaterinstead of a humidifier.

Although the invention has been illustrated and described with respectto exemplary embodiment thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodies within a scope encompassed andequivalents thereof with respect to the feature set out in the appendedclaims.

INDUSTRIAL APPLICABILITY

As set forth above, the humidifier according to the present inventionand the hollow yarn bodies are quite effective as a humidifier and canbe employed in an air conditioner in semiconductor fabrication plantsand clean rooms.

What is claimed is:
 1. A humidifier comprising: upper and lower watertanks supported between the upper and lower water tanks by a supportframe; a plurality of hollow yarn bodies formed of a heat resistant andhydrophilic material which fluidly communicates with the upper and lowerwater tanks, each of said hollow yarn bodies having an external surfacewhich is exposed to a flow of air and forming a thin water film on saidexternal surface; and a plurality of thin metal heater wires adapted forconnection to a power source, each of said thin metal heater wires beingdisposed on the external surface of a hollow yarn body for heating saidthin water film on said external surface for promoting evaporationtherefrom.
 2. A hollow yarn body as set forth in claim 1, wherein asurface tension of the water is used to maintain a film of water overthe surface of said thin metal heater wires.
 3. A hollow yarn bodyformed by winding a thin metal wire as a heater on an outer periphery ofa hollow yarn formed by weaving of a fiber of a heat resistant andhydrophilic material, wherein said heater promotes evaporation of afluid film formed on said outer periphery of said hollow yarn.
 4. Ahollow yarn body as set forth in claim 3, wherein the material of thefiber forming said hollow yarn is a material having heat resistance andhydrophilic property, selected among aromatic polyamide, polyimide,glass, quartz glass, alumina, silica alumina, and aromatic polyester. 5.A hollow yarn body as set forth in claim 2, wherein on the externalperipheral surface, one or more metal wires serving as a heater, arewound in spiral fashion.
 6. A hollow yarn body as set forth in claim 3,wherein the external diameter of said hollow yarn is 0.5 to 5.0 mm, aninternal diameter is 0.4 to 4.5 mm, and the metal wire has a diameter of0.008 to 0.1 mm.
 7. A hollow yarn body as set forth in claim 3, wherein,on the external peripheral surface, an even number of metal wiresserving as a heater, are wound in an alternately intersecting manner. 8.A humidifier comprising: upper and lower water tanks supported betweenthe upper and lower tanks by a support frame; a plurality of tubularbodies formed of a heat resistant and hydrophilic yarn, said tubularbodies fluidly communicating with the upper and lower water tanks sothat a hollow interior of each of said tubular bodies is constantlyfilled with water, each of said tubular bodies having an externalsurface which is exposed to a flow of air and forming a thin water filmon said external surface of tubular bodies; and a plurality of thinmetal heater wires adapted for connection to a power source, each ofsaid thin metal heater wires being disposed on the external surface of ahollow yarn body so as to be covered with a thin film of water, saidfilm being maintained by surface tension in the water and heated by saidheater wires for promoting evaporation.
 9. A humidifier comprising: aplurality of woven tubular bodies formed of a heat resistant andhydrophilic yarn, said tubular bodies fluidly communicating with asource of water so that a hollow interior of each of said tubular bodiesis constantly filled with water, each of said tubular bodies having anexternal surface which is exposed to a flow of air and forming a thinwater film on said external surface; and a plurality of thin metalheater wires adapted for connection to a power source, each of said thinmetal heater wires being disposed on the external surface of a hollowyarn body so that surface tension in the water maintains the wirescovered with the thin film of water, said film being heated by saidheater wires for promoting evaporation therefrom.